text:
Does the EPU on the F-16 need to be manually extinguished after an emergency landing?
After having watched

I noticed at the end that one of his colleagues mention he has a "running EPU with hydrazine, you're gonna need fire response".
Is this just a precaution, or does this fire response actually do anything with the EPU?

The Aviationist has an entire article on this: Hydrazine: A Significant Hazard Each Time An F-16 Crashes (Or Fires Up The Emergency Power Unit). It says:

the impact site of a crashed F-16 can be extremely dangerous and one
  of the main hazards is Hydrazine [...] When activated, the unit
  provides emergency power for the aircraft’s systems in the case of an
  electrical failure: in case of flame-out, emergency power generated by
  the EPU is designed to give pilots the time they need to land the
  aircraft safely. And, the EPU is fired up by Hydrazine.

And (emphasis in the original):

the toxicity of H-70 is such that special procedures must be used to
  manage crashes as well as in-flight emergencies that involved the EPU
  or hydrazine leaks.

The whole thing is too long to quote, but the emergency response team certainly takes some very specific actions to deal with the hydrazine. They isolate the aircraft, give the crew breathing masks to get them away from it, check for leaks and then clean up if needed:

As soon as the first assessment has been completed, the first team is
  replaced by a “response team hydrazine” composed by 2 Italian and 1
  American operator, equipped with special overalls (Level A, since risk
  of contact with the liquid is higher), that clear the leak along the
  track followed by the aircraft from the runway to the parking area.


text:
F-16 low speed SAM avoidance tactics?
After having watched the rather horrible yet fascinating F-16 avoiding multiple SAM launches:

I'm left wondering why he doesn't increase his speed? There are, however, some moments when he's pulling rather high G's where he must have given it some more throttle to sustain any speed at all. Does he need to preserve fuel to get back? Or is it better to maintain somewhat lower speed to have a better turning radius when avoiding SAMs in an F-16?
I understand this is basically asking for an entire lecture in how to avoid SAMs, and I'm trying my best to refrain from doing so. I will keep it to a few specific questions:

Assuming he has the fuel to do so, should he have increased his speed, full afterburner?
Is it possible to see in the video, if chaff/flares are deployed?
Was it wise of him to reduce his altitude by as much as he did, or would he have been safer higher up?

He won't outrun the SAM, so his best option is to out maneuver it.

The missile works by predicting where the airplane will be. If you maneuver, it has to re-adjust, wasting energy.
When the missile has lost enough energy, it'll eventually fail to re-adjust.
Now you can try to beat the missile by being far away and fast
or
you can try to make the missile lose a lot of his energy by doing turns, at low speed. (You can even nodge the missile into the ground by making some close-range, low altitude dives)
In this instance, the pilot was probably already low. Or needed more energy for maneuvering and traded his altitude for energy by descending.

If you maneuver to make the missile bleed off energy, won't your own aircraft bleed off energy as well? It isn't obvious to me that this is something you gain anything by doing. The aircraft is a lot heavier than the missile and bleeds off a lot more energy with each turn than the missile would, on the other hand, the aircraft keeps its engine running, while the missile is probably coasting at least closer to the terminal phase. In any case, it isn't clear to me why this works, and I'm sure not to many other people either.

This works because of 2 main things: the defending aircraft will continuosly be generating energy thanks to it's engine and the missile (depending on the type) will burn a lot shorter, contrary to popular movies. Keep in mind that if the aircraft turns right at 500 knots, the missile will also have to turn right, but aim for a point where it will intersect the aircraft, way ahead of it. It spends a lot of energy doing this. Making further turns will make the missile spend a lot of energy again to try and intersect.

This incident is documented at p. 62 in:
https://www.airforcemag.com/PDF/MagazineArchive/Documents/2016/January%202016/0116packageq.pdf
it is even linked to in the Youtube video, however, these video description fields are not usually that useful, so I overlooked it initially. Sorry about that.
He opted for maneuverability by dropping his fuel tanks, but preserved fuel by staying in military power -- hoping this would be sufficient to survive.

@ymb1 SAM SA-2's (S-75 Dvina, I believe?).

In re Question #1:  No he could not as the jet was probably in full burner at the time of the maneuvers and he needed Max AB plus exchanging potential energy for kinetic energy in a dive to make the jet maneuver at its fullest potential.
In re Question #2:  I can’t see any chaff or flares in the video but it’s very likely he did so as that would be a standard defensive tactic employed if his jet was being shot at.
In re Question #3:  He didn’t have a choice in that situation.  The Viper is doing something called ‘postholing’ ie putting the airplane into a steep, turning power dive and holding the missile perpendicular to his centerline in an attempt to 1) defeat a doppler fire control radar and 2) turn inside of the missile and avoid it.  If given a choice, altitude and airspeed would be preferred; right then more primal survival motivations call for more drastic measures.

I posted an answer to my own question after I realized this: https://www.airforcemag.com/PDF/MagazineArchive/Documents/2016/January%202016/0116packageq.pdf (see p. 62). Apparently he stayed in military power to preserve fuel. However, I accepted your answer, maybe you could update question #1 to reflect the Package Q magazine?

Thanks for the article.  I’ll read over it.

His flares and chaff were inoperative due to some issue

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text:
How do civilian pilots and ATC verify that other people on the radio are who they claim to be?
I am interested in authentication - how identity is verified - in civilian aviation radio transmissions. I know that when someone is speaking on the radio he tells his call sign. But is there any other system that verifies the identity of the person speaking besides just the call sign that he claims to have?
I am interested not only in how ground ATC verifies which aircraft is speaking, but also in how aircraft ensure that they are speaking to a real ATC facility.

Possible duplicate of Is Ground Direction Finding commonly used?

@fooot No, because I am interested not only how ground ATC identifies which aircraft speaking but also how aircraft identify that who is speaking is real ground ATC.

RE how controllers can identify aircraft: Controllers in busy airspace will often request an aircraft to "ident" immediately after their first call. On equipped aircraft, pressing the ident key sends a signal from the aircraft that causes that the blip for that aircraft to flash on the controller's display. This allows them to identify an aircraft. See this question for more on the ident piece

@Geoff Anything similar for aircraft to identify valid ATC?

@vasili111 not that I know of. Nav radios can be verified with audible morse code signatures, but comms are different. Theoretically anyone with a transmitting radio can claim to be a "controller" and there would be no way for a pilot receiving that transmission to verify. This is arguably rare though and would be caught and corrected immediately by the actual controller.

I edited your question to focus on authentication/verification, which I think is your main point. If I got it wrong, please don't hesitate to roll back or edit again. Also, this question and this one may be related.

One case worth mentioning here is Ercan ACC, which from ICAOs point of view is someone (turkish cyprus) setting up a full unauthorized ATC facility. No one is able to stop it because of the political situation on the ground.

In a security setting, this would be called "Man-in-the-Middle Attack", and there has been a great deal of work done on it. That phrase is very search-able...

This is a reasonable question, and to an outside the simple answer of We don't / can't might seem a little bit jarring.
After-all, we live in a time of hacking, terrorism and so on and I can certainly see how this looks like a simple vector to create some havoc.
So, what's to stop somebody from setting themselves up with a Radio Transmitter and deciding to be Air Traffic Control for the day? Absolutely nothing. In fact, lower power handheld air-band transceivers can be purchased legally and cheaply by anyone. I have one near me - I could literally turn it on now and declare myself [Local Airport Tower]
However - the thing about Airband radio is that it's wonderful in its simplicity. At its core is AM radio which is basically unchanged since the early 1900's. This means a few things:

The strongest signal doesn't simply "win". Multiple medium strength signals will simply merge into a garbled mess. This means you don't simply get to "take over" ATC's transmissions - all you can do is ruin them.
Similiar to the above, there's no way (from outside) to stop the ATC signal. All you can do is stomp all over it - something which is totally noticeable.
Even if you do "win over" air traffic control for some aircraft, communications is a two way process, and airband radio is simplex. This means only one person can speak at a time - at some point ATC are going to key in.
Pilots aren't automatons. We listen and build up a picture, we learn normal procedures and can hear stress in somebodies voice. We also know who we were speaking to. Combined with a decent situational awareness, we don't just do things without thinking - you can't just pipe up on the radio and ask an aircraft to fly into the ground.
And even if you did, and they initially believe you, real ATC is going to hear your readback and ask what the hell is going on.

By way of analogy, imagine you've  snuck in on a conference call between an employee and a boss. And you start trying to speak on behalf of the boss - it's going to last all of 1 second before somebody realises something is going on. I think people tend to think of ATC as somewhat robotic, but it's still a human interaction and any good pilot will understand why they're being given instructions.
To attempt to interfere in Air Traffic Control in a way that is believable by the pilots is going to be incredibly difficult. You won't be able to use normal phraseology and cadence if you're attempting to step on real ATC, and that will concern the pilot. To do that for more than a few seconds and to to cause some kind of conflict with multiple aircraft is verging on the impossible.
The most likely outcome is more a denial of service, rather than some kind of spoof. It's not really a great vector to cause any damage. A nuisance, certainly and absolutely dangerous (and there's a reason it's very illegal!) but there are well established procedures for disruption in communications.

I've focused primarily on somebody trying to be ATC here, which is the way in which somebody on the ground would likely go about trying to make a mess. As for pretending to be a plane - firstly there are more technical difficulties because you'll be transmitting Ground -> Ground. I live within 2 miles of my local airport and often struggle to receive their transmissions when I'm at home.
Pretending to be a real plane that currently exists in the sky poses the same problems as above and any facility with RADAR is going to know something isn't right. Again, it might cause some initial confusion but you're unlikely to persuade somebody of something.
You could, in theory, pretend to be a light aircraft with no (or a faulty) transponder but really to what end? I guess you could cause a little disruption before somebody realises you're having a laugh but we're more into the realm of 'pranks' (Not that it's funny) now rather than serious risk.

Comments are not for extended discussion; this conversation has been moved to chat.

could you please add this some place to your answer:  Radio Transmissions are very easy to triangulate even if you are only transmitting a short period. Certain frequencies such as any Air band transmission are going to get prompt notice from many people who have the capability of and motivation to locate your transmission point very specifically.

So let's gloss over the technical details for getting a tower setup that is strong enough to reach far enough to really "drownd out" the proper ATC frequency. And keep in mind that while we are glossing over this, it's not the strongest transmitter wins, two or more transmitters would mesh and just make static and noise. But let's ignore that for now and say that got your setup working, and you're somehow, drowning out real ATC with your own signal.
First ATC is not in control of the plane, so if ATC asked a pilot to do something odd, the pilot can just refuse. There are very, very few instances where ATC has real authority. Mostly that authority is more like, yes you can enter this airspace, or no you can't. Media makes ATC (in movies) seem that it's in control and it tells pilots what to do. In fact, they are more of a service that makes sure planes don't smack into one another. That said if you ignore ATC you had better have a good reason because you're effectively ignoring the "thing" that is telling your X is safe and Y isn't.
Next, there are many "kinds" of ATC, and some of them have more communication with the pilot then others. For example, TOWER and APPROACH "levels" of ATC will talk a lot to pilots as it's their job to make sure planes are landing and taking off safely (glossing over a lot here). GROUND ATC is usually responsible for moving the plain around on the ground at an airport. CENTER level of control doesn't really talk to planes much, they're responsible for, essentially, all the space not around an airport, and generally, don't have much to do with the actual airplane. They don't sit around and go "Yeop your still ok, keep going that way." Though they can talk to planes it's usually to help them avoid other planes and to avoid weather.
Finally, there is the fact that there is a "normal" set of things each level of ATC may ask you to do. For example, GROUND will never tell you to change altitudes, TOWER only controls a very small space around the airport, etc. APPROACH and DEPARTURE may be the most "vulnerable" as they are the ones who handle making sure planes are not running into each other during takeoff and landing. BUT, every airport where it would be a problem has published SIDs and STARS along with approach procedures. So really all ATC does is say "Ok, you're not going to hit someone if you go do the published procedure". There are also published rules on how close planes can get to another. So again, even if you nailed the phraseology, you could not convince a small Cessna to get to close to a Airbus 320. As you stared to do things to move them close together, they would notice they're doing something wrong and refuse.
So while I suppose you could convince a pilot that you were ATC, all you could really do is actually do ATC's job. Not doing ATC's job correctly would just make the pilots go, "Umm, no"

A spoofed "United 123 cleared for takeoff" on a foggy day could certainly cause havoc, though.

@200_success You'd need a really, really strong transmitter to pull that off, since the aircraft would be literally on the field right beside real Tower's transmitter in that case. As soon as you said that, you'd hear "United 123 Stop! Cancel Take-Off Clearance!" And then you'd subsequently be arrested. Likely on some kind of terrorism or attempted murder charge.

Not that I am aware of.  Usual protocol when a call is initiated by a pilot:
who you are calling (Clearance Delivery, Ground, Tower, Approach, Center)
who you are/type of plane
where you are
what you want to do.
Example:
Hanscom Ground, (who you are calling)
Nxxxxx, Cessna Cardinal (who you are and what type plane)
on east ramp with Information Echo, (where you are and that you have the local wind and in-use runway information)
ready to taxi for departure. (what you want to do)
Who you are calling will read back who you are (they may be monitoring more than 1 frequency and not always catch it all), and then proceed from there.
If you don't announce yourself to start the "conversation" you will not be granted clearance into controlled airspace.

But what if someone with radio transmitter will interfere in radio chatter, identify himself as ATC and will send commands to aircrafts? Is there any protection from this?

No. Except real ATC talking and fake ATC talking will interfere and perhaps sound as a squeal over the headset, pilots will ask reply with "stepped on, say again" or something similar until they get a clear response that is along the lines of what expected directions are.

Also 'fake ATC' would need a suitable transmitter, and if they want to be plausible to know real ATC procedures. And you can tall different voices apart on the radio. And fake ATC guy is going to be arrested and have the book thrown at them.

Civilian pilots are identified and tracked in the same manner an any other pilot in controlled airspace - radio communications.  Certain airspace (class E and G) do not require radio communications with ATC.  If no flight plan is on file or activated, they will be unknown targets.
Another means to identify aircraft are, enter establishing ATC communications, they are assigned a specific transponder code which then is associate with their radar returns, making it easy for controllers to know who’s who.

They can track airplane locations, but not the source of radio transmissions, as far as I know:  >From an unknown aircraft waiting in a very long takeoff queue: “I’m f…ing bored!” Ground Traffic Control: “Last aircraft transmitting, identify yourself immediately!” Unknown aircraft: “I said I was f…ing bored, not f…ing stupid!”

I dunno about ATC but ham guys can triangulate the position of a signal if it broadcasts long enough.

Local ATC Tower/Approach won't have that capability, Center maybe. A lone plane flying along won't either.

Re "Civilian pilots are identified...", that's really not the case at all.  All ATC really cares about is targets, not who's flying the plane, or even that your tail number actually matches your call sign.  I've occasionally given my own plane's number out of habit when flying something else, and nobody noticed :-)

@CarloFelicione The only way to triangulate is with access to multiple receivers, equipped with radio direction finding devices. In the UK. at least, lots of facilities can provide a bearing of a signal (E.g., it's coming from 070 degrees) but no single facility can provide a triangulation.
There IS an exception to this, which is the UK's Distress and Diversion Centre who operate a network of radio equipment. But even that relies on the person being visible and generally doesn't operate at less than 1500-2000ft outside of London.

@dan although something like this could easily be adapted for VHF given sufficient coverage.

@Dan, that's the only way to get an instant fix, but if the spoofer continues to operate from the same location for a long enough period of time, then a single person can find him using hand-held equipment. It would be no different from an amateur radio fox hunt.

@jameslarge Of course! I was referring to whether ATC can triangulate or not.

@jamesqf My instructor at one point gave the registration of another of the club's planes at the end of a transmission, and barely realized the mistake even when I specifically pointed it out. We were in the traffic pattern for landing (I think we were doing touch-and-gos at the time). CRM for the win?

@jamesqf Of course, it's likely that nobody notices until something goes wrong, and then your local variety of accident investigation board will want to have a chat with you...

@CrossRoads That bored pilot better hope all other transmissions have been and will continue to be from their fellow pilot. Otherwise, ATC (and/or another pilot) is likely to recognize the voice.

Indeed. Indeed.

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text:
Can a jet engine be restarted after a catastrophic failure?
I have a retired 747 pilot saying that a catastrophic jet engine failure could be restarted. I have little or no training, but I believe that the word "catastrophic" means that there is no recovery. My reference is the 747: The Jumbo Revolution documentary which is on youtube.com and cable TV.

This question is too broad if you can specify a little more on what "Catastrophic" failure they are referencing we may be able to offer an answer. Or if you can put in the time within the documentary of the specific quote in order to provide some context.

I think you've already identified the problem with this question: what does "catastrophic" mean? (Maybe you could link directly to that point in the Youtube video, if it's on there legally?) I think that for most pilots it would mean that the engine is physically damaged and components are broken, in which case there's no way a restart would be possible. But even documentaries like to make things more dramatic, so it's possible that the retired pilot was just exaggerating.

If the document is on Youtube, can you give direct link to the relevant passage? YT allows linking to specific time.

Definitely depends on the definition of catastrophic. If it's ingested foreign debris and caught fire, maybe, depending on how the fire was suppressed. If it's thrown a blade, no way.

I have no desire to dispute what a fellow retired 747 captain said, so I'm wondering if there was some miscommunication between you and the captain.
Or perhaps his definition of catastrophic is different than mine. My understanding of catastrophic would preclude any attempt to restart the engine.
During my time on the 747 I had three engine failures. One simply quit during descent, and I had the flight engineer restart it. One we shut down when the oil pressure started dropping precipitously. There was no thought of trying to restart it as that could well have trashed the engine. Neither of these two shutdowns was catastrophic.
However, on one occasion, shortly after takeoff from Lima, Peru, the #1 engine failed with a loud report, shaking the entire airplane. We were told later that the boom had been heard throughout Lima. The tower reported fire flaring out of both the front and rear of the engine for a few seconds.
After dumping fuel and landing, an inspection of the engine showed a lot of re-solidified melted metal on the inside of the tail cone.
That was a catastrophic failure.

My interpretation of "catastrophic" generally aligns with yours: "A loud bang followed by either a fire or parts of the engine normally required for operation departing either via the exhaust or out the side of the nacelle." -- my assumption is that restarting after such an event is unlikely at best.

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text:
How many fuel pumps does a Katana DA20 have?
How many fuel pumps does a Diamond DA20 have? And since the fuel pump sends fuel to the engine, if you turn it off after the takeoff as the check list says, how will the fuel reach the engine?

How on earth did this get onto the hot network questions list?

it contains good informations :)

Sure; it's just the sort of specialized, technical question that I wouldn't imagine many people would be interested in.

There are 2 fuel pumps on the Diamond DA20. One is electric and is controlled by the pilot and one is mechanically driven by the engine and is constantly running while the engine is running.
After take off, you switch the electric one off and the mechanical one keeps supplying the engine with fuel.

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text:
If an Osprey found itself unable to rotate its engines to vertical, what would be the emergency procedure for landing?
Let's say an Osprey appears to be flying normally in forward flight. In preparation for landing, the pilot tries to command the engines to begin tilting to vertical, but nothing happens. What now?
If there's a manual way to crank the engines up, that's not working either.

I'm not an Osprey pilot, but I'm guessing the procedure is something like "land normally" (i.e. not vertically.)

@reirab Wouldn't the props hit the ground?

I suspect "fasten your seatbelts" would feature strongly in the emergency landing procedure.

@RyanBurnette Ah, looks like you're right. I didn't realize the blades were long enough to touch the ground, even with the prop mounted so high, but it looks like they are. This might be useful information to add to the question.

@reirab That was the purpose of the question. When an Osprey is in forward flight, the propeller disk's lowest point is significantly lower than the extended landing gear. That's why I was wondering what the procedure is if the Osprey can't get it up. I apologize for not being more specific about the V-22's design.

@HowardMiller Yeah, I figured out that that was the purpose after I looked at a diagram and saw that the props would indeed strike the ground. :)

A fixed nacelle landing is an emergency procedure practised routinely in a flight simulator, however actually getting this condition is very rare to date. In short, we reduce gross weight if able, calculate a touchdown speed, fly a shallow approach, and shut down engines after touchdown on rollout.
As for "hanging on the proprotors" in airplane mode, theoretically possible at low gross weights but highly unstable. Besides violating operating limits, the swash plates are locked out in airplane mode giving you no control, not to mention the a few other systems that rely on gravity to pull down instead of back.

Welcome to Aviation.se! Thanks for adding more information about these procedures.

@Creighton you answered another question I came up with later. Namely do the rotors have a collective when in hover mode. This makes it a true helicopter in that mode. I guess another question is whether the Osprey can go into autorotation.

I've seen videos of more conventional aircraft landing with a dead engine, and unable to extend the landing gear. These are two bladed engines. Just before touchdown, the pilot tries to 'bump' the prop to a more horizontal position with the engine's starter motor.

From the bit about "very rare to date", I take it that this has in fact occurred?


text:
What does Top 1% mentioned by ATC refer to?
I have watched Live ATC tons of time. But I still don't know which airline is called "Top 1%". Ex: Delta 81 right Bravo right Kilo give way to company A380 and follow the Top 1%".
Just wanna know what "Top 1%" means. Or that is only for JFK?

Do you have a link to the audio?

Related

I'm guessing you're referring to a clip such as this one. JFK ground is just being a bit informal and fun (as you can tell from the rest of the clip) with their instructions. Although it isn't mentioned, the controller is probably referring to a business jet flight, such as ExecJet.
The "top 1%" refers to a ranking based on income, specifically those not in the lower 99%. The controller is basically telling them to follow the rich people in their fancy private jet. JustSid found another video where the controller explains it as "someone richer than both you and me."

Snarky! Listening to a few other clips of that same atc makes me wonder if it's such a good idea to let Howard Stern take over as ground controller.

@TomMcW it seems to be tradition at JFK and BOS to have snarky ground controllers. :)

Actually, it is mentioned. One of the pilot readbacks is "follow the Gulfstream," so your guess is correct. :)

Here is another "video" which explains Top 1% as "Someone richer than both you and me". So, yep, spot on indeed.

@JustSid thanks, included a link to that one.

Oh yeah. Even thought I cant found the exact video I am saying but this link is also okay. :))


text:
What position was this photo of a jet engine taken from?
From that aviation photographer, I saw that beauty:

Having in mind the jet engine I would see, let's say as a normal passenger, I am not really able to understand from where I am looking at that engine. Do you?
Could it also be that I am looking in an inner part or something (which might explain the confusion)?

PS: I tried using the m character to medium-size the picture, but no luck.

The pressure probe at the top tells you where you are.

If you know about engines, I guess @mins! :)

Based on the Linkedin page, this is a portion of an IAE V2500 turbofan.  Looking at the following images of the engine (in modules and awaiting final assembly), I can pick out a view that is really similar to the image you have up, namely the module of the engine in the bottom right hand corner of the image or the one in the background, behind the fan section that is near the center of the image.

Looking at a cutaway of the V2500 (below), you can pick out similarities between this section and the engine if viewed from directly behind the fan.

Based on this, a schematic of the V2500 engine modules (below), and the insulation laid out in the bottom of the photo that you posted, I think that the picture you found is taken from inside of the engine, directly behind the fan section and looking aft.  The only things that I'm unsure about are background (appears solid?) and perspective (looks like the engine is in a tube--fan was removed, but the shroud is still on?).

The first picture is very enlightening, +1! "picture taken from inside of the engine, directly behind the fan section and looking aft. " What is "aft"? Since, as you see, some parts are still unclear, I will leave the question open for a while, to see if something else comes up. :)

@gsamaras: "Aft" about aircraft and ships is the opposite of "forward" -- that is, in the direction that goes from the nose to the tail of the craft.

Ah that kind of info is superb @HenningMakholm, thanks. Observe however how the depth in "my" image is distorting the linearity of the layers of the parts...

@gsamaras It's not taken "from inside the engine". It's just a picture taken from in front of the engine, after the fan has been removed for some reason. IF you are puzzled about how you could remove the complete fan assembly in one piece (it's big and heavy!) the answer is that you turn the front module (the piece the guy in the red shirt is working on) so it is vertical, and then lift the fan out with a crane.

@alephzero good insight, thanks!

This is IAE V2500 engine inlet (forward section) of an engine without the LP (low-pressure fan), how it' the forward section? just have a look on the NAC TEMP SENSOR which is going to be always placed in front of the engine. Cheers :)

photo source :https://www.alamy.com/stock-photo-closeup-of-the-air-inlet-of-an-iae-v2500-turbofan-engine-39488888.html

The answers agree, that's good.


text:
Why the different wing and tail designs in similar sized jets vs turbo prop?
I was flying on Porter Airlines and they had an info card about how similar the Bombardier (I still say DeHavilland) Dash 8 Q400s are to the Bombardier CSeries they have ordered.
There was a cool overlay photo to show relative sizes and shapes:

Looking at that image, it got me wondering about the straight vs angled wing.  Straight vs angled tails, etc.
I get that a jet is faster than a turbo prop.
Cseries cruise speeds are:
Mach 0.78 (828 km/h, 447 kn, 514 mph)
Dash8 Q400 cruise speeds are:
414 mph (667 km/h) 360 knots
Those are pretty close and yet that is a pretty radical wing design change.
Is this just the history an old design (Dash 8) vs a very modern design?

Hint: M.60 is quite different from M.82. ;)

Well, for starters, the speeds are actually pretty significantly different. The Cseries is almost 25% faster than the Q400. Swept airfoils are much more efficient at those higher speeds, as are jet engines.
The Q400 is also a wildly stretched version of the original DeHavilland Canada DHC-8 (Dash 8), which was itself based on the 4-engine DHC-7 (Dash 7) STOL airliner. DHC has a lot of history building short takeoff and landing aircraft with pretty extreme performance, and a lot of that colored the design of the Dash 8. What you see today in the Q400 is the result of about 70 years of backcountry aircraft design, applied to a commuter airliner.
The Cseries, on the other hand, is a clean-sheet Bombardier design meant to compete with the E-jets and the smallest 737s (and 717).
Hopefully that answers your questions!

For some more info on why swept wings tend to show up as you get above about mach 0.7 or so, check out the Wikipedia article on swept wings. You'll even find a reference there to a swept-wing transsonic propeller driven aircraft - the TU-95 which has a top speed around the same as the C series,

Even more fun, the Tu-114 airliner was based on the Bear and could carry up to 225 passengers. They're pretty absurdly fast turboprops, and I think their engines are some of the most powerful in the world.

As I recall they're also allegedly one of the loudest aircraft in operation - I've never had the pleasure of listening to one take off, but judging by the size of that propeller disk it would not surprise me if this were true.

@voretaq7 Isn't the noise caused by the tips going supersonic rather than the size per se? (Sure, longer blades mean that the tips will go supersonic at lower rpm.)

@DavidRicherby Yup - and that's the reason large blades are potentially noisier (it's harder to balance "efficient RPM for the airfoil" with "please don't be making sonic booms"). You also get a larger "whoosh" as each blade goes by (moving comparatively more air than a smaller-diameter prop at the same RPM), but i's the noise off the tips that tends to dominate.


text:
What is the round thing on the tip of an MD-90 wing?
I like to pretend I know about airplanes, but have always wondered what the round things on the tip of MD-90 wings are. Here is an image of what I am talking about:

To be clear, my question is what the round, hole-like item is in this photo. It is on the trailing edge of the wing facing backwards. My current best guess is that it is the hole that the smoke comes out of when Delta is using the planes for sky-writing and doing other cool loop-de-loop type tricks. I have yet to see the smoke come out...

When has Delta ever used an MD-80 (or any other plane) for sky writing? They certainly don't use it for aerobatics...

Sky-writing? loop-de-loops? Smoke?   You're smokin' sometin', thats for sure, Murenrb.   SMH.

(It's a joke...)

Yes, a joke. Only people lacking a sense of humour would not recognise it as a joke. I like jokes, they lighten up our lives.

This is a logo light. The MD90 as originally delivered to Delta didn't have these.

This is the wingtip light arrangement on an airplane without the logo light.

Thanks for answering! I never knew logo lights were a thing. Now I do! Learning!

It looks like a recognition/logo light or aft white position light.  An MD-88 has a combination aft white position light and white strobe light assembly that is installed in the trailing edge of each wing tip.


text:
How do tyre pressure sensors in aircraft work?
I am specifically interested in the sensors used on the B777 and B787.

On a Boeing 777, a tire pressure sensor/fill valve is installed on each of the 12 main gear wheels and two nose gear wheels. There is an in-axle transformer in each of the axles.
The tire pressure sensor/fill valve is made of an air fill valve and three independent pressure sensing channels which provide accurate tire pressure.
The tire pressure sensor/fill valve is installed in the wheel.
A relay transformer hubcap assembly connects to the tire pressure sensor/fill valve. The left 28V DC MAIN bus supplies the electrical power to operate the tire pressure indication system.

(Image source: 777 AMM)
You can see the sensor in these images:

(Source: airliners.net)

(Source)

They both use a tire pressure monitoring system (TPMS) from Crane. Crane's marketing materials on the system are available on its site, and this newsletter from Boeing confirms it:

The software group helped with testing on a new  tire pressure and brake temperature monitoring system on the 777 for  Boeing  supplier  Crane  Aerospace  &  Electronics.

(Since Boeing confirms that they work with Crane at all, I that doubt Crane would lie about its involvement in the 787 -- that seems like a good way to tick off what I'm sure is a major customer!)
Crane doesn't describe the system in great detail on its site, but from the name ("SmartStem") and description ("wireless tire pressure
sensor with integrated fill valve") it appears to be a Direct TPMS sensor installed in the tire's valve stem. From Wikipedia:

In most current designs of direct TPMS, a small electronic assembly which is rugged enough to be mounted inside a tire, measures the pressure using a microelectromechanical system (MEMS) ...

In short: there is a sensor on the valve stem that translates the air pressure to a mechanical process, probably using a piezoelectric sensor or similar. This information is then wirelessly transmitted to the rest of the plane's systems.

I worked on the TPIS and BTMS during the years 1992//1993, but the manufacturer and designer was LABINAL the french company located near Paris !


text:
Are student pilots required to have spin entry and recovery training?
Do trainee pilots learn to enter into spins and recover from them in any basic trainer aircraft? Does any regulation mandate this?

Depends where you are.  US doesn't. Canada does.

Germany does, Iceland doesn’t. So not even the same within EASA.

Which country's regulations are you asking about?

Aircraft I trained in was prohibited from spins as per its POH, so spin training would have been quite illegal using it.

Some instructors in the US teach spins to students seeking private pilot SEL despite it NOT being currently required in US.  Your question could possibly be reworded to recognize the possibility that there may be no universal answer-- for example you could ask do ALL trainee pilots learn to enter... or do ANY trainee pilots learn to enter...   etc.  I experienced one flight dedicated to spin entries and recoveries in the US despite it not being required-- we did not wear parachutes and the instructor said that was fine as long as I was possibly considering get an instructor rating sometime

US used to, I recall doing spin & recovery 3 times in a Cessna 150 Aerobat (in 1994), and feeling queasy for quite a while after that. I think now those maneuvers just need to be demonstrated. See AC 61-67C, excerpt follows

CHAPTER 3. FLIGHT TRAINING: SPINS
  300. SPIN TRAINING. Spin training is required for flight instructor-airplane and flight instructor-glider applicants only. Upon completion of the training, the applicant’s logbook or training record should be endorsed by the flight instructor who provided the training. A sample endorsement of spin training for flight instructor applicants is available in the current edition of
  AC 61-65, Certification: Pilots and Flight and Ground Instructors.
a. Spin training must be accomplished in an aircraft that is approved for spins. Before practicing intentional spins, the AFM or POH should be consulted for the proper entry and recovery techniques.
b. The training should begin by practicing both power-on and power-off stalls to
  familiarize the applicant with the aircraft's stall characteristics. Spin avoidance, incipient spins, actual spin entry, spin, and spin recovery techniques should be practiced from an altitude above 3,500 feet AGL.
c. Spin avoidance training should consist of stalls and maneuvering during slow flight using realistic distractions such as those listed in Chapter 2. Performance is considered unsatisfactory if it becomes necessary for the instructor to take control of the aircraft to avoid a fully developed spin.
d. Incipient spins should be practiced to train the instructor applicant to recover from a student's poorly performed stall or unusual attitude that could lead to a spin. Configure the aircraft for a power-on or power-off stall, and continue to apply back elevator pressure. As the stall occurs, apply right or left rudder and allow the nose to yaw toward the stalled wing. Release the spin inducing controls and recover as the spin begins by applying opposite rudder and forward elevator pressure. The instructor should discuss control application in the recovery.
e. Spin entry, spin, and spin recovery should be demonstrated by the instructor and repeated in both directions by the applicant.
(1) Apply the entry procedure for a power-off stall. As the airplane approaches a stall,
  smoothly apply full rudder in the direction of desired spin rotation and continue to apply back elevator to the limit of travel. The ailerons should be neutral.
(2) Allow the spin to develop, and be fully recovered no later than one full turn.
  Observe the airspeed indicator during the spin and subsequent recovery to ensure that it does not reach the red line (VNE).
(3) Follow the recovery procedures recommended by the manufacturer in the AFM or
  POH. In most aircraft, spin recovery techniques consist of retarding power (if in a powered aircraft), applying opposite rudder to slow the rotation, neutralizing the ailerons, applying positive forward elevator movement to break the stall, neutralizing the rudder as the spinning stops, and returning to level flight.
f. During spin training if a spin is not fully developed, the aircraft may instead go into a spiral. A spiral may be recognized by a rapidly increasing airspeed after the attempted spin entry. In an actual spin, the airspeed normally stabilizes below stall speed). The pilot must recognize a spiral and initiate immediate recovery to prevent exceeding structural limits of the airplane.

SPIN TRAINING AND PARACHUTES. Title 14 CFR part 91, § 91.307(c) prohibits the
  pilot of a civil aircraft from executing any intentional maneuver that exceeds 60° of bank relative to the horizon, or exceeds 30° nose-up or nose-down attitude relative to the horizon, unless an approved parachute is worn by each occupant (other than a crewmember). Section 91.307(d) states, in part, that § 91.307(c) does not apply to flight tests for a Pilot Certificate or rating, or spins and other flight maneuvers required by the regulations, for any certificate or rating when
  given by a certificated flight instructor (CFI) or an airline transport pilot (ATP) instructing in accordance with part 61, § 61.167.

a. Section 61.183(i) requires an applicant for a Flight Instructor Certificate airplane or glider rating to receive flight training in stall awareness, spin entry, spins, and spin recovery procedures. The applicant must also possess and demonstrate instructional proficiency in these areas to receive the certificate or rating.
b. Because spin entry, spins, and spin recovery are required for a Flight Instructor Certificate airplane or glider rating, a person receiving instruction from an authorized instructor need not wear an approved parachute while instruction is being provided in these maneuvers.
The instructor providing the training is also not required to wear an approved parachute while providing this flight training.

I did my Private Pilot training in 1994 in the USA. There was no spin requirement for Private Pilots in 1994. Spins do not need to be demonstrated for any checkride; CFI candidates need a logbook endorsement of spin training, that is all.

So did I, started in April 1994. We definitely went up that summer to 4500 ft, the highest I had been in my private pilot training. My instructor did a spin, we recovered, leveled off, climbed back up, and then I did two myself, and felt queazy the rest of the day.  My wife got her private in 1996, and only had it demo'd.

Regarding this part of the regulation: "unless an approved parachute is worn by each occupant (other than a crewmember)". Do I understand it correctly to mean that the pilot and instructor don't have to wear parachutes but anyone else who comes along for the ride does? (Second question: What sort of crazy person comes along for the ride?)

Many planes are only approved for spins in the Utility Category.  For my Cessna Cardinal (177) for example: "UTILITY CATEGORY
This airplane is not designed for purely aerobatic flight. However, in the acquisition of various certificates such as commercial pilot, instrument pilot and flight instructor, certain maneuvers are required by the FAA. All of these maneuvers are permitted in this airplane when operated in the utility category.
In the utility category, the baggage compartment and rear seat must not be occupied.
Chandelles, Lazy Eights, Steep Turns, Spins, Stalls."

So no parachutes, and no passengers.

See the first sentence in your quote: instructors need it, but nobody else does.  I don't recall exactly when the rule changed, but it's possible your instructor in 1994 was still following the old rule.

My instructor had an Aerobat and was a great guy, flying for one of the regionals when I last heard from him (a while ago now).  He may have asked if I wanted to go do spins in his plane, my C-150 (this was before I bought the Cardinal, C-177) might have been in the shop or something. He used to do interesting things to be distracting and keep us on our toes. I don't recall the specifics leading up to the flight any longer.  No idea when the rule changed either.

Just found this article that states "Accidents like this one further a debate that has divided the aviation community since 1949, when the Federal Aviation Administration eliminated from the syllabus for a private pilot’s license the requirement for spin training. "  “We saw that 48 percent of the fatal accidents from that era involved stall/spin, and of those the majority were training-related. We were killing people in trying to eliminate the very thing that was happening to them.”  https://www.airspacemag.com/flight-today/the-spin-debate-3571421/

Two more: "In 1976, the FAA published the results of a study (FAA-RD-77-26: “General Aviation Pilot Stall Awareness Training Study”) that were the justification for its policy that teaching people to avoid spins in the first place is a better means of saving lives than teaching people to get out of them. That policy was further refined in 1991 (Advisory Circular 61-67B) and in 2000 (61-67C), but not fundamentally changed. Statistics seem to support the FAA’s judgment."

Last one: "The 1976 report states: “More fatal and serious injuries have occurred from stall/spin accidents involving general aviation aircraft than from any other single type of accident.”  When I did my Biannual Flight Review this summer, I only had to demonstrate Power on (for takeoff) and Power off (for landing) stalls.  My Cardinal has micro vortex generators, so it doesn't stall very much, the nose just bobs a little; dropping the nose a little with power stops the stall so you really have to work at getting it to stall. Then just be careful not to overbank when turning base to final.


text:
Is it possible to overheat or damage the engine on an F-16?
The MiG-25 can supposedly damage its engines by commanding too much thrust and gaining too much speed. Somewhere around mach 3 damage to the engines is likely, I believe.
What about the F-16?
What happens if the pilot, at altitude, attempts to simply go as fast as it will go?
I believe the F-16 has FADEC (Full Authority Digital Electronic Control). The MiG-25 does not. I imagine this would limit the amount of fuel flow by some limit.
However, even if this is true, is it still possible for the pilot to exceed the ordinary limits imposed by the computer?
As a bonus question, it would be interesting to also mention if this does or does not apply to other fighters, in particular the F-14, F-15 and F/A-18.

I'm interested to hear the answer to this. Intuitively, it seems foolish that a military plane would be limited to a non-damaging regime as mission success may well include outcomes with damaged engines or even destroyed aircraft which it seems it would be foolish to prohibit in a non-civilian context.

The Panavia Tornado's RB199 engines have a system called 'datum' operated with a 2 position switch, low and High. This basically allows the engine more temperature in the combustion chamber and, consequently more power.
Downside is it drastically reduces the life of the engine and incurs a big maintenance penalty every time it was used. It was soon inhibited in the Low setting and safety wired.

Yes, you can overheat and damage an F100 or F110 engine just like any other jet engine.  It has mechanical and thermal limits that may not be exceeded.  And it often happens as part of high performance military flying, though it can make you very unpopular with your crew chiefs and inevitably with you commanding officers if you keep willfully exceeding the limits and damaging engines.
FADEC systems ie “power by wire” systems just use a computer to administer engine control commands based on pilot inputs.  They do not necessarily limit a flight crew from giving inputs that can exceed engine parameters.
Earlier engines were more finicky about this, in particular to exceeding hot section temperature limits or compressor stalls.  The F-14A with the TF-30 engines was particularly prone to compressor stalls and could be treacherous during critical phases of flight.  Improved intake diffuser, gas core aerodynamics, advancements in materials science and manufacturing plus improvements to fuel control units reduced the risks but did not eliminate them.

Very interesting. Any stories that could be references of F-16 engines being damaged from too aggressive use?

Of course you can.
It's exactly the same situation as on the 787 or A320.  If you insist on always using full 100% thrust for every takeoff and all the way through climb-out, you will cause excessive wear to the engines, resulting in inevitable early failure.  The system doesn't stop you from doing this, because for all it knows, you are flying a marginal situation and need all that power to stay alive.
This is a "safety system vs. safety system" type problem, like whether you should have a "low water level shutoff" on a diesel fire pump.  The shutoff might save a \$50,000 engine by sacrificing a \$50,000,000 warehouse.
End of the day, even on an A320, you make it pilot discretion.  You bet your bippy the F-16 does exactly the same thing.  Yes, you can and should abuse the F-16 engine when it's necessary for safety, however that also gives you the freedom to abuse the engine when it is not.

"If you insist on using 100% power", of course we know the other extreme, leading to a stall on climb out.  Although a safe climb out at less than 100% power can be pre-programmed with a lower rate of climb, are jet pilots really discouraged to push safety limits to "save" the engines?


text:
Why is air traffic control done manually by humans?
I'm not a pilot but have a software developer background, so forgive my aviation naivety.
From what I understand there have been numerous issues and almost-issues relating to human air traffic controllers. Not to mention there is considerable cost and complexity required for this delicate system to work perfectly all the time.
My question is simply why do humans manually attempt to guide all aircraft in real time? Has computerized air traffic control ever been suggested, and maybe even attempted? What was the problem?
Before anyone says that air traffic control is computerized; that's not what I mean. I mean fully computerized, with digital communication between the aircraft and a central computer on the ground which continuously updates the aircraft FMS, OANS (On-Board Airport Navigation System) or similar, and autopilot with all the required information and directs aircraft as needed with optimal real time sorting and queuing.
As for more simple aircraft without FMS, OANS or other suitable systems, perhaps they are better suited for having human guidance for the foreseeable future. A speech to text interface to a computerized tower would probably be disastrous.
It seems, (probably naively) to me, that this would eliminate a lot of latency, a lot of cost, and a lot of complexity. As an aside, this appears would also give the pilot contextual awareness if desired (I cannot imagine this would be useful during normal operations), as the OANS would be able to display everything the tower can see.
Having it explained to me briefly what exactly the tower does that cannot be handled by such a system would probably enlighten me somewhat.
My own reasoning for why this isn't a good idea:
The only thing I can think of is, I can imagine that sometimes information is relayed to the tower that requires some use of context and best judgment that would be hard to implement in full in software. Perhaps there is an emergency, and the pilot needs information about advice for some ad hoc emergency landing.
However, if this is the problem, the extreme cases where a human is preferred, why not keep a few humans around, similarly to how aircraft without OANS would perhaps need humans, just in case one is needed. The vast majority of the mundane work that seems (again probably naively) incredibly better suited for a computer to deal with, be handled by, a computer?

@ymb1 Done. Thanks.

@ymb1 This also illustrates my lack of knowledge on the subject matter quite well.

You may also read about anticolision system such as T-CAS that automated part of ATC work

There is a great deal of "if it ain't broke, don't fix it" involved.  ATC existed long before computers were capable of handling an automated system - if indeed they are today.  (As both a software developer and a pilot, I wouldn't bet on that :-))  Then there is the cost of retrofitting all the airplanes with equipment capable of data communications, and displays to make that info available to pilots.  And of course all the equipment has to be FAA certified, which makes it expensive.  Compare the cost of an aviation GPS vs the one in your cell phone, for example.

@ManuH TCAS does not automate part of ATC work! It is a safety barrier that is intended to prevent a collision when all else failed.

It's NP hard but humans know good enough approximate solutions intuitivly.

You know, in contrast to your question OP, as a software engineer my first assumption would be "well it's inconceivable that will ever be automated" - !  Automated systems for things like playing Go or driving a car on a road are conceptually simple. But it would seem imposisble to ever automate air traffic control. (It would be like saying "Could we automate the Senate?" say!)

Except CSX was running their entire national system from a NORAD-in-the-movies style video-wall control center back in the 90s when ATC was still pushing cards around (they quit doing that, right?)  I'm sure now it's all on VR helmets lol...

The idea to automate ATM functions is moving on, particularly when planning the use of drones which is going make airspace more busy. FAA works with MITRE Corp on traffic management modernization. This MITRE document (any some other easily found) gives some idea of the problem to solve, and possible solutions: Controller-Automation Interaction in NextGen: A New Paradigm

Having it explained to me briefly what exactly the tower does that cannot be handled by such a system would probably enlighten me somewhat.

Fair warning, that's my job you're trying to replace with a computer, so I'm probably biased. Still though, hear me out:
What do we do?

Handle a large amount of non-standard requests and communication between the cockpit, the airport, the airlines, flight schools, fire and rescue, authorities and many other parties
Deal with vehicles or even individual persons moving on the maneuvering area, where the only available communication is an (analogue) handheld radio
Identify obstructions or animals (such as birds) on and around the airport
Deal with smaller general aviation aircraft with no sort of digital communication, only a radio. Sport aircraft, gliders, hot air balloons.
Deal with individual aircraft without transponder (not visible on radar). A digital system would have no way of knowing where the aircraft are.
Handle traffic at entire airports without radar coverage. A digital system would have no way of knowing where any aircraft are.
Deal with aircraft with no flightplan (only way to know what the pilot wants is to talk on the radio)
Make decisions not only based on what is said, but also how it is said. It's quite easy to notice an inexperienced trainee pilot on the radio, and they need a bit more space and might not always do what they're told
Setting the runway lights to an appropriate level based on a number of factors (darkness, visibility), some of which are not easily measured digitally
See, visibly, when an aircraft enters or leaves the runway (most airports don't have ground surveillance, so the only way to determine the position of aircraft is to look out the window)

Could these things be solved/handled by a computer? In theory, sure. You could:

Invent some sort of artificial intelligence that intuitively knows exactly what someone means as they say it, and know who to forward the message to.
Replace all aircraft vehicles worldwide with fully autonomous, self-driving Teslas that can communicate with a central control system.
Install a number of high definition cameras on every airport worldwide, and use artificial intelligence to classify visible objects. Then alert the self-driving Teslas to go and scare the birds away.
Force millions of hobby pilots and flight schools worldwide to invest thousands of dollars in new equipment that can communicate with a new digital ATC system (before that: actually invent that equipment, and get it certified worldwide)
Force millions of hobby pilots and flights schools worldwide to invest thousands of dollars in transponders. Invent new light-weight batteries that enable the installation of transponders in light weight aircraft, gliders and hot air balloons.
Install thousands of new radar stations worldwide. Invent a way to deal with garbling and FRUIT caused by all the new radars.
Force all pilots to file a flightplan prior to flying. Change the flightplan format so that it is much more accurate than it is today, and teach all pilots worldwide the new format. Force all small, single-engine planes to always be flown by two pilots: one will fly the plane, the other will be busy on the iPad, changing the flightplan in real time as the flight progresses, since a short message over the radio is not an option (a digital system wouldn't understand it)
Assume the worst case scenario for all flights. Add extra separation between all aircraft. Reduce capacity at many airports by 50%, thus increasing delay by millions of hours worldwide.
Install a light control panel in the cockpit of every aircraft in the world. Teach all the pilots to use it, install redundancy systems in case it fails.
Since we've already made everyone buy transponders, why not install ground radar in every airport in the world? Will probably only cost a few million dollars per airport.

Last but not least, invent the system that actually processes all this data, to replace the decision making that is today done by air traffic controllers. Have it work in every single edge case, in every airport, in every type of climate and weather conditions, with every aircraft type, with every type of flight - and have it certified by aviation authorities worldwide.
Anyway, I think you see where I'm going with this. Is training air traffic controllers expensive? Yes. Do humans make mistakes? Yes. Would creating and getting certified a new digital system be cheaper? Absolutely not. Would it be safer? In the long term, maybe marginally. In the short term - most likely the opposite.

You may be biased, but those are some of the major points I thought of and IANAPORATC (I am not a pilot or air traffic controller).

I've accepted your answer. Thanks for enlightening me. Would you say it is fair that humans would benefit from having a computer system that attempted to sort and queue in real time, with humans keeping their jobs, for exactly the reasons you've specified -- but a computer that handles the tasks that can be handled, with humans verifying the sanity of the operation?

@AlphaCentauri That already happens to a large extend. We have many computer systems to help with various tasks. AMAN/DMAN and MTCD are good examples.

expeditedescent, I had to upvote you, if only for the "Fair warning" statement, but this is a great answer. Signed: a retired ZDV controller...

I’ll note that some of what you list is already available via CPDLC and ADSB, just not ubiquitous. And if there’s even one aircraft that doesn’t have it, you still need humans in the loop.

You did a great job explaining many of the complexities of ATC. I will add just one more: weather.

In 2024 there’s a new potential answer: replace the ATC operator with an LLM coupled with high definition cameras in each airport. I predict this will happen by 2050.

@JonathanReez I respectfully disagree. LLM's are famously bad at math, which you absolutely need in ATC. But actually, IMO ATC could be automated with current technology (no fancy AI needed). The problem is that a lot of the data required to make decisions simply isn't digitally available (see points 2-7 in my answer). The lack of digital interfaces will be the limiting factor - not computing power. (And bear in mind that an automated system must be compatible with theoretically every single aircraft in the entire world. It's not exactly a controlled environment)

@60levelchange LLMs and math has been fixed for a year now :-) With a couple more decades of effort they’ll make it good enough to replace most intellectual human labor.


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How is the JFS manual hand pump operated on an F-16?
The JFS (Jet Fuel Starter) on an F-16 allows for two attempts to start the engine.
https://www.quora.com/How-do-you-start-the-engine-on-an-F-16-Fighting-Falcon
However, if this fails, there is a manual pump that can be operated:

Where is this pump? Inside the cockpit? Hidden in some hatch outside? How is it operated? How long does it take to build up enough pressure for one more attempt to start the engine?
As a bonus question: Surely the JFS system can be charged with external equipment rather than this hand pump? What is that procedure called?

Meower68 left a comment on this answer explaining how it worked:

WRT comments about the F-16 JFS. Hydraulic pressure from accumulators, not compressed gas, starts it spinning. You have two such accumulators; you can dump one and, if it fails, dump the other and try again. You can dump both at once, providing more time for the JFS to engage. If you've dumped both, without success, you can put a t-shaped handle on an double-acting hydraulic pump in the port wheelwell and MANUALLY repressurize the accumulators and try again. Doing so is roughly equivalent to 150 or so push-ups; extremely exhausting. Ask me how I know :-) – Meower68 Jun 22 '17 at 20:58

I'll be damned, that's almost exactly the drill on a CH-46 APU start but only one accumulator tank.

I used to be a crew chief on F-16s in the Air Force. Our pilots usually jump both bottles at once during a start up to ensure a proper start, if it fails it's most likely because there wasn't enough pressure accumulated. It's part of our launch procedures before they take off to check to see if it's within limits, if not you have to get the "T handle" and go manually pump it up to pressure. This is done in the left hand wheel well there's a big slot for the handle to be inserted and pinned into to keep it in there while you pump. There's a gauge on the opposite side under a quick access panel to check the gauge. Usually if we do have to pump it you'll pump for awhile and take a look at the gauge and keep going back and forth to check it. We rarely hook anything up to automatically charge it, it's manual 9/10. Actually, it usually takes 15 min to charge however some people are slower or even faster, it's more on the person to determine how fast it charges. It's very tiring to do it.


text:
Are any jet engines used in combat aircraft water cooled?
Are any jet engines used in combat aircraft water cooled?
If they are not, and instead are air cooled, how can the engine ensure consistent cooling? Wouldn't the airflow passing through whatever radiator implementation it has be greatly affected by the airspeed? Consider low subsonic numbers with heavy maneuvering in a dogfight, vs. mach 2 sustained flight?
While I can imagine that variable air inlet for the radiator would change the airflow, I really have no idea how this would work.
I'm also aware that certain rocket engines, e.g. the F-1 allow the fuel itself to circle around the thrust chamber to cool it. Perhaps a similar system is used in jet engines.

Jet engines are cooled and temperature managed by the mass air flow itself which is used to surround and limit the boundaries of the flame, keeping it away from the burner can walls, and dilute the heat of the flame as it passes to the turbine (only a minority of the mass airflow's oxygen is actually burned - which is why afterburners work; there's lots of leftover oxygen to work with).
If you're talking about using a closed liquid cooling system with heat exchangers taking heat from the burner can and turbine somehow, well, I've never heard of a water jacketed burner can, and how you could use liquid in a closed system to cool a turbine, who knows.
Liquid cooling was used in the past as supplemental cooling to increase available power by spraying water directly into the mass flow as mentioned here, but in that case the water is a consumable.

Don't forget that the Harrier also uses water injection...

Actually, the most important part of temperature management is fuel supply.

From the standpoint of temperature as a limit on power yes, and when your ITT margin is gone, your engine is worn out.  Here we're really talking about a "temperature control system" used as coolant as it were, and in that case it's really just clever management of the air flow surplus to oxidation requirements.

The thing most in need of cooling inside a jet engine is usually the high pressure turbine blades.  The air entering the first stage of the turbine is in the neighborhood of 2500F (https://en.wikipedia.org/wiki/Turbine_blade). This is often higher than the melting temperature of the blades themselves. These blades are cooled using air bled off from the high pressure compressor, which is typically at a "cool" temperature of 1000F or so.  Water would not be much help in cooling here, as it would instantly vaporize.
EDIT:
@hobbes I was about to say the same thing.  Beyond that, where does all of the water come from? You'll have to bring it with you on the plane.  Based on data from here (https://leehamnews.com/2017/01/27/bjorns-corner-aircraft-engines-operation-part-2/) a CFM56 core has a mass flow rate at cruise of about 50 pounds/s.  1-3% of that is used for turbine cooling, so let's just call it 1 pounds/s.  So during a two hour flight, you are using about 7200 pounds of air for cooling.  Let's say that water is 10x efficient at cooling, so if you replace air cooling with water cooling, you need to carry 720 pounds of water along with you for each engine, plus a tank to store it in, a pump, and tubing.  Overall at least 1500 pounds increase to overall aircraft weight.  That means you can either carry less passengers (less revenue) or have to carry more fuel (more expense).  That's a big hit versus air cooling which is basically free in terms of weight.

On the contrary, water would be (from a thermal perspective) much better at cooling, since it starts out at a much lower temperature, it consumes a metric forktonne of heat in the vapourisation process, and all that comes way before it gets merely as hot as the cooling air usually used starts out as.

Water would need to be at a very high pressure to keep it from boiling inside the turbine blade. That makes the construction (which is rotating at 10,000 rpm, remember) heavier. Pumping water from the stationary part of the engine to the rotating shaft would require a seal that has to withstand hundreds of bar, which is difficult to achieve. Even filling the cooling passages with water instead of air would add considerable weight.

The closest I could find for closed-cyle fluid cooling was a 1975 NASA study for supersonic aircraft, but this used no radiators, and wasn't for the engine.  Instead, circulating refrigerant moved heat from the wing and fuselage to the fuel tank containing liquid hydrogen, in the hope that titanium skins could be replaced with cheaper aluminum.  The conclusion was that this would help only at airspeeds much greater than Mach 3.
Even for piston-powered aircraft (and NASCAR automobiles for that matter), the drag due to airflow through a radiator can be enormous.  Some 1930's racing aircraft used radiators inset flush to the wings for this reason.
It may just be that the jet engine's mass airflow suffices, so there's no justification for the extra complexity and weight of a dedicated heat exchanger.

A radiator doesn't have to produce a large drag penalty, or even any drag penalty at all - in fact, a properly-designed radiator can actually produce net thrust, by using the air it heats as reaction mass.

Neato!  ...it looks like the Meredith Effect has been tried in Formula 1 cars, but not in jet aircraft.  Answered another way, because a turbine's combustion isn't blanketed in an enclosed cylinder head, maybe the nonmoving metal parts don't heat up enough to warrant liquid cooling - the airflow is enough.  (Sending coolant through the turbine blades seems ghastly complicated.)

@CamilleGoudeseune Most jet aircraft do send coolant through the turbine blades, but the coolant is gas not liquid. See https://aerospaceengineeringblog.com/turbine-cooling/ for pictures.

Good grief, I had no idea that modern turbine blades look like ant farms.

The KC-135 used to have water cooling during takeoff to increase thrust during a critical phase of flight (decreasing runway required and increasing max weight).  When the KC-135 transitioned to the R-model, the new high bypass engines no longer required water cooling.
The MQ-9 is a combat aircraft, and has a turboprop, and therefor is technically a jet.  The extended range variant uses an alcohol-water injection system for takeoffs at high gross weights in certain environmental conditions in order to provide cooling for max thrust at takeoff.

If you mean liquid cooling like the piston engine in your car then no, as stated above boundary layer air cooling is used to keep vanes cool, shape the flame in the combustion chamber to stop it touching anything. There is a large amount of air available and means to control it.
 The Pegasus engine in the Harrier uses water methanol as a thrust augmentation system, cooling the compressor air, making it more dense, making more power.
See here :-  How does jet engine water injection work?


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What is the procedure for restarting an F-16 in the air?
If there is a flameout on the F-16 in the air, what is the procedure for restarting it?
I'm sure this is an elaborate checklist, so I'm only asking for an overview of the key parts, especially I'm interested in to what extent the pilot has to manually operate this process.
Is it required to manipulate fuel? Ignition? Temp? Air source? Does it involve the JFS system? Battery?
This https://www.quora.com/How-do-you-start-the-engine-on-an-F-16-Fighting-Falcon provides a nice little overview of how to start an F-16, with some pictures. However, it doesn't explain exactly how the engine is ignited in the first place. JFS, then engage throttle to allow fuel in, and magically it ignites? Surely it doesn't ignite just from pressure alone when driven by the JFS? It feels like a crucial step is missing in that overview and that step would probably allude to how to restart the engine.
It seems that in the event of a flameout, on at least block 50 F-16's Can fighter aircraft glide? the EPU (Emergency Power Unit) kicks in which provides power and hydraulics. Prior to this, the battery supplies power (but I imagine it must be turned on manually, as there is a switch for this!) and the hydraulics appear to work for some time even without the EPU, JFS or the main engine.
However, I know nothing about how the engine actually gets restarted. What does the pilot need to do, and why?
As a bonus question: Why doesn't this guy attempt to restart the engine? Did they already try, and give up?

First, press Ctrl-Alt-Del...

I'm sure the pilot did try to restart and could not due to a mechanical failure or had run out of fuel, you'd never glide land a fighter voluntarily.

Wasn't there an F-16 crash recently? I guess quicker answering is required here... :)

@rackandboneman Belgium lost an F-16 during an exercise in France, September 23rd.

There are a lot of questions rolled into one here, and I can't answer specifically to the F-16, but a turbine engine needs the same three elements from the basic fire triangle to run:  Fuel, Air, Ignition.  The element missing from the sequence description linked in the question is ignition.
The igniters are like spark plugs, and they are probably energized during actuation of one of the other mentioned switches.  Most likely the JFS switch has a secondary function of energizing the ignitors since it is engine start specific.
Airstarts are not an overly complex procedure, in fact for a single engine aircraft like the F-16 they need to be brief and committed to memory because fighters don't have the best glide ratio.
Fuel - Make sure the throttle wasn't inadvertently shut off, likely the checklist will call for placing this in the idle position.  (you need fuel flow, but don't want to dump too much gas into an engine that isn't lit yet!)  Perhaps there is a step to turn on a boost pump or switch tanks.
Air - Airborne this comes from outside ram air pressure, as measured by airspeed.  The minimum airspeed required envelope will vary with altitude, but most pilots will have a number committed to memory that will provide reliable airstarts across a broad range of altitudes.
Ignition - There will likely be a separate igniter switch for airstarts.  Press and hold until lightoff is achieved, then advance the throttles smoothly and resume flying.  The airstart ignitor switch is generally located on the power control lever for convenience.  If single engine, an alternate electrical power source may be required first in the form or activating a Ram Air Turbine or other source of emergency power to provide a spark if the generator is disabled.
The process isn't really any different from lighting a natural gas stove or propane grill that has a piezoelectric lighter - You turn on the gas and hold the button down or press repeatedly to make the igniter spark until it lights, then release the button and adjust the flame.  (in fact when testing the airstart igniters on the ground before flight you listen for a clicking sound to indicate they are sparking!)
So, in its simplest form a generic airstart checklist for a tactical jet would look something like the following example:

AIRSPEED - Maintain 200 KIAS minimum.
THROTTLE - Idle.
AIRSTART BUTTON - Press and hold until light off.
If no relight by 5000 feet AGL - EJECT

Very nice answer. What if the engine doesn't rotate quite as smoothly as it should? Perhaps it ingested foreign material and can turn, but not enough to relight at 200 KIAS? Wouldn't it be a good idea to use the JFS in attempts to force the engine up to a higher RPM?

Good question.  In the twin jet I flew the procedures said to NOT attempt an airstart if severe mechanical damage was suspected due to the risk of fire.  This could be different for a single engine jet.  I did fly the single engine TA-4J in training years ago and could reference the manual later for a generic answer, but I'm afraid I can't do anything more than speculate on how an F-16 should respond in such a situation.


text:
How is an x-ray image taken of a combat airplane?
At 7:31 in the following Youtube video (the link should start at 7:31, t=451):

There is an x-ray image being shown, of (I presume) part of the guts of an F-15.
How are these pictures taken? What machines are used, what are they called?

Radiography is used in many different applications. One relevant example is shipping containers. So, radiography on a fighter really isn't that difficult.

One reason to X ray a fighter aircraft is that a maintenance technician lost a tool. A screw driver or wrench being slammed around during a high G turn can do a lot of damage. Maintenance Technician have to account for every tool after working on a plane. If a tool is missing they do everything possible to find it.

This is done by the NDI shop. Non Destructive Inspection.

NDI is responsible for ensuring the integrity of aircraft structures by utilizing multiple inspection methods such as eddy current, magnetic particle, radiographic and ultrasonic.

https://www.15wing.af.mil/News/Article-Display/Article/2919599/ndi-the-plane-docs/
Digital radiography

"The new digital X-ray system is really cool and fun to work with, providing a faster way to develop and read an image,"

https://www.tyndall.af.mil/News/Article/712369/x-ray-vision/
large-standoff/large-area thermography (LASLAT)

large-standoff/large-area thermography (LASLAT), an advanced thermal
imaging tool that has expanded the capabilities of non-destructive
inspection (NDI).

Thermographic inspection can use either a component’s inherit heat flow (passive thermography) or an induced heat flow (active thermography) to reveal component abnormalities.

https://www.compositesworld.com/news/ncms-report-demonstrates-thermography-innovations-for-enhanced-ndi-capabilities

I know it's not what you directly asked, but a lot of medical imaging technologies scale up surprisingly well and find application in industrial settings. The synergy is quite a natural one - a boroscope inside a jet engine is basically a surgical tool in a different setting, after all!
I'm a medical physicist, and if you gave me a fighter jet and probably about $10m I could manufacture and build from scratch a multi-energy CT scanner to scan it with – and the system would have remarkably little major modifications to existing human (or veterinary) equipment. There are a number of industrial companies that offer such services – both X-rays, ultrasound and CT are routinely used in industry for non-destructive testing as it really lets you verify what welds are doing in the finished part. The main difference is that (for X-rays) the source and the detector are both portable, or (for CT) you tend to keep the beam and detector fixed and move the sample around in 3D slowly (if possible) rather than building a hangar-sized gantry (although large ones do exist). A cheap, portable X-ray machine you can buy on Alibaba looks like this: the X-rays come out of the top and you then put a film (yes, film!) plate some distance away that you then develop. The film doesn't have to be flat (though it usually is) and the X-rays come out in a cone (probably):

One of the other "nice" things about imaging materials rather than people is that the radiation doses they can handle are far larger radiation dose and therefore imaging with other techniques than (living) biological systems could manage. Ignoring for the moment the fact that some highly bright national-level X-ray sources specifically support aerospace imaging, neutron imaging techniques come to mind: neutrons interact with matter differently and can provide information that is harder to obtain with X-rays.
Phoenix WI are a US-based neutron imaging organisation who have some beautiful images showing ceramic contamination within cooling channels in turbine blades via both X-rays and neutrons:

The manufacturing of jet engine turbine blades is one particular industrial niche for neutron radiography. Turbine blades are cast around ceramic molds which form cooling channels that prevent the blades from melting when exposed to the high temperatures of their operating environments. In manufacturing, fragments of ceramic can clog these cooling channels. A blade with clogged cooling channels could break or even melt while in operation, so such flaws must be rooted out with 100% certainty. The X-ray image (left) cannot clearly depict the cooling channels in a batch of blades; however, the channels show up much clearer in a neutron image of the same batch (right).

X-ray:

Neutron:

These differences can be made even more clear by using gadolinium as a contrast agent – something that I do routinely in patients, where Gd3+ ions chelated to various other compounds (such as DOTA) form the basis of most contrast agents in MRI because of their paramagnetic properties – by soaking the turbine blade in gadolinium-containing contrast, any (porous) ceramics left behind show up brightly:

This sort of QA informs the manufacturer about how good their QA/QC processes are and how effectively made their turbine blades are. Making jet parts is difficult, they're often at the limit of the material's properties in basically every way at once and the consequences of an unplanned failure in a high-demand environment (e.g. at take-off) can be fatal. Modern radiographic imaging techniques have a lot to offer aviation beyond weld inspection – one of the reasons we've got so much better at building high-performance, fuel-efficient and complex aircraft is because we can prototype everything digitally, model what happens to it, manufacture it to micron tolerances, and then prove that what we have made is what we have modelled and everything ties up. Radiological techniques fill in the bit in between and tie the loop together between design and manufacture.


text:
How does F/A-18 autotrack work?
This is about the alleged "UFO" video. However, I'm not interested in speculation about what exactly the aircraft being tracked in the video is.
What is "autotrack" in an F/A-18 Super Hornet? Does it involve tracking by the radar, infrared, or digital interpretation of the video stream by a computer?
I've provided a link to the video. This shows the aircraft (the alleged "UFO") being "tracked" by what the pilot claims to be "autotrack":

As a bonus question, what is the other pilot asking about? He asks "Did you box a moving target?", what does it mean to "box" a moving target? Does it refer to radar tracking?

Autotrack means the FLIR (Forward Looking InfraRed) sensor attempts to track whatever object falls inside the tracking area. It means whatever the pilot was trying to keep up with was producing emissions in the infrared (heat) and the system was automatically tracking it.
Boxing a moving target is having the tracking system detect and track a target you have selected. In this case, the other pilot was asking if he had selected the target manually (boxing) or if the system detected and autotracked the target on its own.

Thanks. Although from this explanation it seems like boxing the target is exactly what the pilot in the video did.

Well, what the pilot did was maneuver the aircraft to allow the targeting computer to use its sensors to present him with a "boxed" target display. A very long time ago i was part of the team at Hughes Aircraft Company that developed the F-14 Tomcat RIO display (back seater). That box was amazing. It could track 12 targets at a time, from acquisition to destruction, and inside all it had was two Intel 8088 CPU's, the same as the very first IBM-PC. And no math coprocessor!

I see, thanks. The F-14 RIO has two 8088's that are programmable, when developing software for it? I wasn't aware the 8088's were found in SMP configurations. Very interesting.

8088's are general purpose CPU's, you write the code, they just run it. Like I said, it was an amazing box.

I have experience writing x86 assembly, although not for the 8088, but dealing with two physical CPUs in an SMP system typically requires an APIC or similar to handle inter-process interrupts and similar issues that are needed to manage an SMP system. I'm just surprised that such a simple CPU as the 8088 had a working SMP ecosystem with all the required hardware and software support required to have two parallel execution threads to do useful work --- not to mention in an F-14!

All I can tell you is what I posted. I can't get into any further details of the internals... other than it was mostly written in PL/M... and frankly, that was 36 years ago, just a little while after I completed my stint with the Marines. A lot of neurons have been sacrificed to the Jack Daniels' god since then, so my recollection is not so hot. I can tell you that I tried to solve their math coprocessor problem (all their math was table driven) by suggesting the use of the NEC V20 CPU. But that did not fly because it wasn't manufactured in the US.

I would be surprised if the two 8088's were used in an SMP architecture. More likely would be one handles the sensor data and passes that data to the other chip to perform the tracking.

@selectstriker2 Agreed.

@JuanJimenez cool! And thanks for serving!


text:
For what reasons might a taxiway be mistaken for a runway?
In this article, an airliner landed on a taxiway instead of a runway. What might be the reasons that a pilot can mistake a taxiway for a runway?
(I mostly know the answer for this question, but I want to see what you guys can find out too as well as making a reference point for others.)

http://www.skybrary.aero/index.php/Wrong_Runway_Use

2017-07-07 incident involving five airplanes: http://edition.cnn.com/2017/07/11/us/air-canada-flight-runway-trnd/index.html

Essentially, some taxiways look very like runways and they might even be more visible to pilots in certain conditions. That leads the pilots to focus on the taxiway rather than the runway.
In 2007 the FAA commissioned a study into ways to avoid pilots landing on taxiways, with special emphasis on KSEA (Seattle-Tacoma). One of their goals was to address exactly the scenario in the article you linked to:

Find a solution for the Seattle-Tacoma International Airport (SEA-TAC)
  problem by  identifying possible visual aid enhancements to prevent
  pilots from mistakenly  identifying taxiway Tango as the adjacent
  runway 16R as a landing surface.

The study mentions several reasons why pilots mistake taxiways for runways:

A pilot will generally associate an air traffic control (ATC) instruction such as “cleared to land runway 16R,” with their visual presentation of the runway configuration. In other words, pilots see a taxiway where they expect to see a runway: this was a particular problem at KSEA because until the third runway was built, it had 16L and 16R, with taxiway T located to the right of 16R. Therefore a pilot landing on 16R would see three 'strips' with taxiway T as the rightmost one and might assume it was 16R. KSEA now has 3 runways with taxiway T between 16R and 16C.
Some taxiways look physically very like runways, i.e width, surface material, square edges etc.
Some taxiways stand out more clearly in low light conditions because their surface is lighter than the runways
Sun glare can hide runway and taxiway markings so that pilots can't tell the difference visually

There's also an FAA engineering brief that explains how to identify potential problem taxiways, it gives essentially the same information as the study.
Both documents say that the most important point is to alert pilots in advance about the potential problem by giving warnings via ATIS, charts and so on. That's especially true for pilots who aren't familiar with the airport, and GA pilots make more mistakes than airline pilots so presumably training and general currency/professionalism as well as having at least 2 pilots in the cockpit makes a difference too.

You should put more emphasis on squared-off ends on taxiways -- this is probably the single largest visual presentation problem a taxiway can pose re: TWY/RWY confusion.

Here's a shot of a more or less correct approach to Liverpool Airport (lined up a little outside):

Image Source
This is in clear daylight VFR conditions. Notice the taxiway to the right; long, straight, flat, and very runway-like. If the conditions weren't as clear and you were in a pattern where you crossed by the taxiway first, you might mistake it for the runway.
Here's a circling shot of DFW International from the southeast, almost in line with 31R to the right of the picture:

Source: Wikipedia
Each runway has a full-length or near-full-length taxiway, and because of the heat, movement count and weight considerations of the planes it regularly sees, all surfaces at the airport are concrete to minimize maintenance and resurfacing needs. Even on the normal north-south approaches, it can be difficult in some VFR conditions (with no approach lighting) to distinguish the runways from adjacent taxiways. The outlying diagonal 13/31 runways are worse in some regards as their taxiways are full-length and nearly as wide as the runway itself, and they have, in some circumstances, been used as runway surfaces, so the taxiway has a few tire scuffs and jet blast marks at the expected places for a runway. If you can't clearly see the threshold marker due to glare, it's not hard to at least line up for the taxiway and have to go around once you realize your mistake closer in.
In general, landing on a taxiway is more likely to happen:

When the pilot is unfamiliar with airport layout, including student flights, diversions and recent renovations
When the taxiway looks similar to the runway, i.e. same surface material and similar length/width
In IMC at smaller D/E airports with poor/grandfathered lighting
When the taxiway and runway layout or materials are opposite pilot expectations (e.g. taxiway outside the runway relative to primary terminal/hangar facilities)
When the taxiway is the runway, or has been recently or regularly (during maintenance of the usual runway surface, or when abnormal aircraft movement counts require additional runways, like Oshkosh during EAA AirVenture)
When a low-altitude, shallow glide slope approach is required which reduces the aspect angle and thus the ability to identify critical runway markings on long finals

Mistaken identity is generally less likely:

In clear nighttime conditions when approach lighting is clearly visible (the runway will be unmistakably bordered in white with standard approach lighting including strobe arrays and green end lights, while most taxiways will be bordered in blue with minimal additional lighting and not easily visible from the air)
When taxiways are clearly differentiable from their adjacent runways in length, width, material and pathway (other answers mentioned deliberate "chicanes" added to taxiways so it's obvious from the air that's not a landing surface; taxiways intentionally running at an angle to offer a different compass heading on approach are another option, but rare as this requires increased land area)
When the pilot is well-educated on, and/or personally familiar with, the airport's runway/taxiway layout
When a normal and/or steep glide slope is recommended, thus giving the pilot a high-aspect look at the complex.

As Air Traffic Controller, I can say that there are many reasons, but mostly:

Unfamiliar airports.
Poor visibility during taxi in and taxi out.
Low situational awareness.
Poor signage on airside.
Bad judgement from the crew.

How is Taxi-in / Taxi-Out visibility related to this at all?

Confusing a runway with a taxiway is quite possible when talking about visibility. Instead of turning to enter on the taxiway/runway, the crew can continue the taxi, misjuding the right exit, and performing an incursion.

One airport with a history of taxiway/runway confusion is London Gatwick where 26R/08L is used as a taxiway most of the time, only being used as a runway during maintenance of 26L/08R and emergencies.  Crews have even mistaken taxiway Juliet for the runway.

We should treat runway incursions separately. As asked, this questions seems about accidental landings off-runway. Entirely different problem with totally different causes & solutions.

@curious_cat Not sure who your comment was for, but Gatwick has had several instances of take offs/landings from taxiways, either 26R/08L or Juliet.  Juliet even had an artificial kink built into it to help with identification at night.

There are often low clouds/fog around SEA (the airport, specifically).  I work along the southern end, and there are many days where you can't see planes that just took off (or on approach).

Taxiway "A" at the approach end of runway 29R has the words TAXI on the taxiway.  Many A-10 and F-16 pilots over the years have mistaken the parallel taxiway with the runway.  The primary is the approach is a LOC BC and as such is a little more difficult than standard for training pilots.  They look up at MDA, right of center-line and see a long "runway" and not the taxiway.
KTUS Aerial map runway 29R

I've personally trained pilots who have lined up on a taxiway.  Two things were apparent, they were both visual approaches with no instrument backup to reference and they both looked up assuming the runway was right in front... like it always is.
One pilot commented he can't imagine a pilot mistaking a taxiway for a runway till he was circling one day and lined up on the parallel taxiway to the circling runway.  We talked about it afterwards, he said. "Wow.  I swore that was the runway.  I identified the runway and my perception made it so... even though it wasn't.  I need to take more time to confirm what my perceptions are telling me."

Pondlife has an excellent answer.  I just wanted to add that at some (very few) airports, the taxiways are specifically constructed as an alternate landing surface, for emergency use in case the main runway is shut down.  In this case, the taxiway could look very similar to the main runway, just without the appropriate markings.
Additionally, in theory an airport could be expanded, and old runways could be transitioned to be used as taxiways.  This would make them look physically similar, again without the normal markings.
My own technique is to always have the ILS tuned up for the runway I am landing on (if there is one at that runway), even when doing a visual approach to prevent just this (or prevent landing on the wrong runway if there are multiple parallels).  Lining up on the wrong piece of concrete should show up pretty clearly on the ILS, especially when very close in.


text:
Why are aircraft registration details made public?
Recently, a friend asked me why aircraft registration details are made public since related car license plate numbers details are more regulated in access by law. Me, being an avgeek and taking this for granted, do not know why this is. Why are aircraft registration details made public?

It's quite useful for finding certain kinds of international crime, like arms dealing https://yorksranter.wordpress.com/2005/06/27/all-the-viktor-bout-stuff-is-here/ or the CIA rendition flights.

Aircraft registration are no more or less public than car registrations (although they are a bit easier to get access to). Generally speaking you can go down to the DMV and request data on a plate number, for example here is the form for doing it in PA (there is a fee involved). Since cars are registered by state its up to the states how this works, planes however are registered federally and thus governed a bit differently, the FAA provides a nice portal here for looking things up.
From the FAA...

In accordance with the underlying statutory framework (49 USC Chapter
  441) and as described in the applicable SORN, the information
  maintained in the aircraft record is available to the public upon
  request. This is to facilitate aviation safety, security, and
  commerce, the main purpose for which the record system exists. The
  public nature of the aircraft record allows for title searches by
  prospective buyers and/or financiers of aircraft purchases as well as
  for other interested parties to gather information concerning the
  aircraft including its airworthiness. The existence of recorded liens
  against the aircraft as well as the priority of those liens can be
  determined by a careful review of the documents maintained in the
  aircraft record.

This is done for a few reasons, first off many things in aviation may be billed by tail number. For example if you fly into an airport, say KPNE which has a city imposed 5$ landing fee, and the FBO for some reason does not collect this. The airport needs a way to look you up to send a bill. The FAA may also do this to make it easier for non-federal employees (local police etc) to access information related to an aircraft.
For what its worth the FAA also lists pilot data pretty freely, however you can now elect to hide your personal data (but not your name)in the FAA portal.

That's basically how government databases work. Grants and amateur radio licenses expose plenty of information.


text:
Why is the MD-88's front starboard door smaller than its port one?
Having been on a few airplanes of the MD-80 family, I noticed that the front starboard doors of the planes were smaller than the ones on the port side. Why may this be the case?
This may also be the case with the rest of the DC-9 and B717 family as well, but I don't remember that clearly anymore about those other planes.

You may want to ditch the Port/Starboard terminology

The larger port side doors are for extra convienience during boarding. Passenger boarding is always done on the port side (left) while the starboard side doors are only used for servicing the galleys or as an emergency exit.

So it is just because of the traffic through the doors?

Yes. On some aircraft I have flown the starboad side doors were so small you would have to stoop over to get through.